This 1963 photo released by the American Alpine Club Library shows the American Mount Everest Expedition team and their sherpas on the world’s highest mountain. They reached the roof of the world May 1, 1963, a decade after Sir Edmund Hillary.

BERKELEY, Calif.— It might be hard to conceive now, in an era of extreme sports and ultra-light equipment, but there was a time when Americans who set out to conquer mountains engaged in a pursuit that was as lonely as it was dangerous.

But four men — Norm Dyhrenfurth, now 94; Jim Whittaker, 84; Tom Hornbein, 82, and Dave Dingman, 76 — remember. The leather boots that stayed wet for weeks. Oxygen canisters that weighed 15 pounds. The shrugs of indifference most of their countrymen gave a half-century ago to what it would take to get a U.S.-led mountaineering expedition to the top of Mount Everest.

“Americans, when I first raised it, they said, ‘Well, Everest, it’s been done. Why do it again?’” Dyhrenfurth recalled as he and three other surviving members of the 1963 expedition gathered in the San Francisco Bay area for a meeting honoring the 50th anniversary of their achievement.

The American Alpine Club is hosting lectures, film screenings, book-signings and a dinner this weekend recognizing the pioneering climbers and what their feat, captured in a Life magazine cover story, came to represent in the years after President John F. Kennedy honored the Everest team with a Rose Garden reception: the birth of mountaineering as a popular sport in the U.S.

“When they were talking about a reunion three years ago, I thought, who the hell cares about that? I figured we’d just get together for some beers,” Dingman said between interviews with National Geographic, Outside magazine and the Alpine Club’s oral history project. “It’s turned into this big event, and I’m glad it has.”

Whittaker, who lives in Seattle and went on to become chief executive of outdoors outfitter Recreational Equipment Inc., was the first American to summit Everest. He and his Sherpa companion, Nawang Gombu, reached the top of the world on May 1, 1963, a decade after New Zealand’s Edmund Hillary and about six weeks after another climber on the U.S. expedition, Jake Breitenbach, died in an avalanche.

Memories of how close he came to his own death on Everest — he and Gombu ran out of oxygen on the summit and had to climb up and back without water after their bottles froze — infused every day of his life since with gratitude and child-like wonder, he said.

“I think I will probably take it with me into my next life, if I have one,” Whittaker said.

Three weeks after Whittaker’s ascent, two other Americans, Hornbein and the late Willi Unsoeld, became the first men ever to scale Everest via a more dangerous route on the mountain’s west side. The next day, they descended by the southern route that Hillary, Whittaker and by then, two more members of the American team, had taken to the summit.

The adventure, which included spending the night without sleeping bags or tents at 28,000 feet, made them the first men ever to traverse the world’s highest peak — and cost Unsoeld nine frost-bitten toes.

Dingman has been lauded over the years for sacrificing his own chance to scale Everest to belay Hornbein, Unsoeld and two other climbers, Barry Bishop and Lute Jerstad, who had gotten stuck out in the open with them, back down to base camp.

Dingman never made it back to Everest. As a doctor in training, a Vietnam War draftee and then a physician with a young family, he never could find the time to make the trip. He said he had no regrets then and has none now.

“It would have made no difference to get two more people on to the summit, but if we had lost two or three people on the way down that would have been a very different story,” he said.